Kivy:如何通过 id 获取小部件(没有 kv) [英] Kivy : how to get widget by id (without kv)

问题描述

假设我在 Kivy 中动态定义了一些小部件(按钮)并动态分配它们的 ID.在这个用例中我没有使用 kv 语言.我可以在不跟踪小部件本身的情况下保留小部件 ID 的引用:然后我想通过它的 ID 访问小部件.我可以做类似通过 id 获取小部件"之类的事情吗?(如果我在 kv 文件中定义了小部件，我可以使用 self.ids.the_widget_id 通过其 id 访问小部件本身)

Let's say I define on the fly in Kivy a few widgets (buttons) and dynamically assign their id. I'm not using kv language in this use case. I can keep a reference of a widget id without keeping track of the widget itself : then I'd like to access the widget through its id. Can I do something like "get widget by id" ? (If I had defined the widget in a kv file, I could have used self.ids.the_widget_id to access the widget itself through its id)

推荐答案

Kivy 小部件制作树形结构.任何小部件的子级都可以通过 children 属性获得.如果需要，您可以只保留对根窗口的引用，然后使用 walk 方法迭代它的小部件:

Kivy widgets make tree structure. Children of any widget are avaiable through children atribute. If you want, you can keep reference only to root window and then iterate over it's widgets using walk method:

from kivy.app import App
from kivy.uix.boxlayout import BoxLayout
from kivy.uix.button import Button 

class MyWidget(BoxLayout):
    def __init__(self, **kwargs):
        super().__init__(**kwargs)

        button = Button(text="...", id="1")
        button.bind(on_release=self.print_label)

        l1 = BoxLayout(id="2")
        l2 = BoxLayout(id="3")

        self.add_widget(l1)
        l1.add_widget(l2)             
        l2.add_widget(button)

    def print_label(self, *args):
        for widget in self.walk():
            print("{} -> {}".format(widget, widget.id))

class MyApp(App):
    def build(self):
        return MyWidget()

if __name__ == '__main__':
    MyApp().run()

walk() 和 walk_reverse() 方法被添加到 Kivy 1.8.1 版本的 kivy.uix.widget.Widget 中.对于旧版本，您需要自己递归解析树:

walk() and walk_reverse() method were added to kivy.uix.widget.Widget in 1.8.1 version of Kivy. For older versions you need to recursively parse tree yourself:

from kivy.app import App
from kivy.uix.boxlayout import BoxLayout
from kivy.uix.button import Button 

class MyWidget(BoxLayout):
    def __init__(self, **kwargs):
        super().__init__(**kwargs)

        button = Button(text="...", id="1")
        button.bind(on_release=self.print_label)

        l1 = BoxLayout(id="2")
        l2 = BoxLayout(id="3")

        self.add_widget(l1)
        l1.add_widget(l2)             
        l2.add_widget(button)

    def print_label(self, *args):
        children = self.children[:]
        while children:
            child = children.pop()
            print("{} -> {}".format(child, child.id))
            children.extend(child.children)

class MyApp(App):
    def build(self):
        return MyWidget()

if __name__ == '__main__':
    MyApp().run()

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